There was some talk earlier that tag stats pages (e.g. stackoverflow.com/questions/…) will contain info about creator & creation date, but it hasn't been implemented. (And yeah, it wouldn't be the same as what you suggest.)
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JonikJun 30 '09 at 21:06

Although this is marked status-declined, it is possible for a tag you've already won Taxonomist for. Simply click the Taxonomist badge in the bottom section of your main profile page to be told which tag it was awarded for.

Alternatively, use this URL:http://SITE_NAME/badges/11/taxonomist?userid=YOUR_USERID

I think the concern here is that if people know what tags they have created they might start using it on dubious questions to try and get the Taxonomist badge. I could definitely see that happening, considering as it is some people do know they created a tag and push it on questions sometimes.

Other than that, I can definitely remember thinking I created a juicy one months ago but I can't remember what it was for the life of me, so I would like to know.